The Collaborative International Dictionary of English v.0.48:

Nunchion \Nun"chion\, n. [OE. nonechenche, for noneschenche,
   prop., a noon drink; none noon + schenchen, schenken,
   skinken, to pour, AS. scencan. See Noon, and Skink, v.
   i.]
   A portion of food taken at or after noon, usually between
   full meals; a luncheon. [Written also noonshun.]
   --Hudibras.
   [1913 Webster]